This invention relates to machines for manufacturing cardboard boxes and, more specifically, relates to a machine with stabilizers that prevent the pressure applicators from tilting when they partially overlie a web of corrugated board.
Machines for manufacturing corrugated board may include a segmented hold-down structure consisting of a grid of pressure applicators including a number of rows, each including a number of individual pressure applicators. These pressure applicators press a moving web of corrugated board against a heated platform, such as a steam chest, to dry the board and set the glue as the web of corrugated board is propelled through the machine. In a belt driven machine, the pressure applicators directly press against a conveyor belt, which in turn presses the board against the steam chest, as the conveyor belt propels the board through the machine. In a beltless machine, the pressure applicators press directly against the corrugated board, which is typically pulled through the steam chest section of the machine by a vacuum or belt drive located downstream from the steam chest.
For either type of machine, segmenting the pressure applicator structure into a grid of pressure applicators allows the number of rows engaging the board in the direction of machine flow to be varied in response to the speed of the machine and the thickness of the corrugated board. In addition, segmenting each row of pressure applicators into a number of separate pressure applicators in the cross-machine direction allows the number of pressure applicators engaging the board to be varied in response to the width of the corrugated board. In addition, the pressure applied by the pressure applicators in the cross-machine direction may be varied to apply a desired pressure profile to the board.
An inexpensive yet effective pressure applicator structure including passive pressure applicators is described in commonly-owned U.S. Pat. No. 6,390,963 entitled xe2x80x9cCorrugated Board Manufacturing Apparatus Including a Preheater Section with a Variable Heat Transfer System and a Hotplate Section with a Passive Hold-Down Mechanism.xe2x80x9d In this machine, the downward pressure applied by the pressure applicators are not actively controlled. Instead, the pressure applicators are individually weighted to impart a desired pressure profile on the underlying board. The use of passive pressure applicators eliminates much of the machine""s control system, which results in an inexpensive machine that is east to set up and operate.
In this type of machine, one or more pressure applicators at each end of each row typically include actuators, such as air cylinders, to independently lift a corresponding pressure applicator off the underlying board. This feature allows the machine to accommodate less than full-width board. Typically, each row includes eight hold-down pressure applicators with the outermost two pressure applicators at the end of each row including independent lifting actuators. This allows the center four, the center six, or all eight hold-down feed to engage the corrugated board of varying width.
With this type of machine, however, the pressure applicators pressing down against the edges of the corrugated board do not always overlie the board completely. In particular, when less than half of a pressure applicator overlies the edge of the board, the pressure applicator can tilt. When this happens, the edge of the board can be pinched, and a portion of the board may not receive adequate downward pressure. This causes the board to be manufactured improperly, which results in waste board. In addition, the pressure applicator may press the conveyor belt against the steam chest, which can quickly destroy the conveyor belt.
Therefore, a need exists for a segmented pressure applicator system that prevents individual pressure applicators from tilting when incompletely overlying a web of corrugated board.
The present invention meets the needs described above in a machine for manufacturing corrugated board that includes a heated platform and a conveyor for propelling a web of corrugated board adjacent to the heated platform in a machine direction. The machine also includes a row of pressure applicators aligned substantially transverse to the direction of machine flow and configured to press the web of corrugated board against the heated platform. To prevent the pressure applicators from tilting when incompletely overlying a web of corrugated board, the machine includes a stabilizer configured to prevent a corresponding pressure applicator from tilting while applying pressure to the web of corrugated board.
Each pressure applicator may be independently weighted, and the weights of the pressure applicators may be selected to impart a desired pressure profile to the web. The machine may also include a lifting apparatus for lifting a corresponding pressure applicator independently of the other pressure applicators. In particular, the stabilizer may include a connector, such as a flexible strap or rigid bar, securing two pressure applicators to each other. For example, the connector may secure a right end pressure applicator to a left end pressure applicator. And a second connector may secure a right second position pressure applicators to a left second position pressure applicator. In this case, the right second position pressure applicator is typically located adjacent to the right end pressure applicator, and the left second position pressure applicators is typically located adjacent to the left end pressure applicator.
To remove pressure from the web, a support bar configured to lift a row of pressure applicators may be moved from a lower position to an upper position. The support bar is configured to lift the pressure applicators above the corrugated board when moved to the upper position, and to permit the pressure applicators to move vertically with respect to the support bar when moved to the lowered position to remove the weight of the pressure applicator from the support bar and to apply the weight of the pressure applicators to the corrugated board. To implement the stabilizer, a support structure is coupled to a pressure applicator, and one or more alignment members are supported by the support bar and configured to limit lateral movement of the support structure to permit the support structure to move vertically with respect to the support bar while preventing the pressure applicator from tilting.
For example, the support structure may include a support surface and one or more alignment members supported by the support bar and positioned adjacent to the support surface to limit lateral movement of the support structure while permitting the support structure to move vertically with respect to the support bar. Each support structure may include one or more support surfaces and one or more alignment members positioned adjacent to the support surfaces. For example, the support surface may be defined by the edge of a support plate, and the alignment members may include one or more alignment blocks or rollers.
More specifically described, a first embodiment of invention includes a machine for manufacturing corrugated board including a heated platform and a conveyor for propelling a web of corrugated board adjacent to the heated platform in a machine direction. The machine also includes a row of pressure applicators aligned substantially transverse to the direction of machine flow and configured to press the web of corrugated board against the heated platform. To prevent the pressure applicators from tilting when incompletely overlying a web of corrugated board, the machine includes a first stabilizer including a connector securing opposing end position pressure applicators to each other to prevent the end position pressure applicators from tilting while applying pressure to the web of corrugated board. The machine may also include a second stabilizer including a connector securing opposing second position pressure applicators to each other to prevent the second position pressure applicators from tilting while applying pressure to the web of corrugated board. Typically, each second position pressure applicator is located adjacent to a corresponding end position pressure applicator. The connector may include a flexible strap or rigid bar connecting support structures to each other. Each support structure, such as an xe2x80x9cLxe2x80x9d bracket, is typically attached to an associated pressure applicator.
A second embodiment of the invention includes a machine for manufacturing corrugated board including a heated platform, a conveyor for propelling a web of corrugated board adjacent to the heated platform in a machine direction, and a row of pressure applicators aligned substantially transverse to the direction of machine flow and configured to press the web of corrugated board against the heated platform. The machine also includes a support bar selectively supporting the row of pressure applicators that may be moved from an upper position to a lower position. The support bar is configured to lift the pressure applicators above the corrugated board when moved to the upper position, and to permit the pressure applicators to move vertically with respect to the support bar when moved to the lowered position to remove the weight of the pressure applicator from the support bar and to apply the weight of the pressure applicators to the corrugated board. The machine also includes a first support structure coupled to a pressure applicator, such as a right end pressure applicator, and one or more alignment members supported by the support bar and positioned to the first support structure to permit the first support structure to move vertically with respect to the support bar while preventing the right end position pressure applicator from tilting.
The machine may also include a second support structure coupled to a left end pressure applicator, and one or more alignment members supported by the support bar and positioned adjacent to the second support structure to permit the second support structure to move vertically with respect to the support bar while preventing the left end pressure applicator from tilting. The machine may also include a third support structure coupled to a right second pressure applicator, and one or more alignment members supported by the support bar and positioned adjacent to the third support structure to permit the third support structure to move vertically with respect to the support bar while preventing the right second position pressure applicator from tilting. The machine may also include a fourth support structure coupled to a left second position pressure applicator, and one or more alignment members supported by the support bar and positioned adjacent to the fourth support structure to permit the fourth support structure to move vertically with respect to the support bar while preventing the left second position pressure applicator from tilting.
In various alternatives, each support structure may include a support surface and an alignment block positioned adjacent to the support surface, a support surface and one or more rollers adjacent to the support surface, two support surfaces and one roller adjacent to each support surface, two support surfaces and two rollers adjacent- to each support surface, or two support surfaces, two rollers adjacent to one of the surfaces, and one roller adjacent to the other support surface. In addition, each support structure may comprise a support plate attached to the pressure applicator.
The specific techniques and structures employed by the invention to improve over the drawbacks of prior pressure applicator structures and accomplish the advantages described above will become apparent from the following detailed description of the embodiments of the invention and the appended drawings and claims.